Inner tube



June I 14, 1938;

R. s. TAYLOR e-rm.

INNER TUBE Original Filed Nov. 16, 1932 ZSnventor RAYMOND 5. TAYLORPHILIP M. TORRANCE ROBERT M flNZ/ijjf? attorney:

PM June is, less UNITED STATES 2.120.310 Inseam: I Rum-iamimrnmpiia'rmeemwcrtEAndermAkromOhimudsnontoThe-Fheatone'1|re&llnbber0ompa r,'Akron,

ohiaaclrporationoflmh ormmu am November 16, 193:, mu

Divided This invention relates to-inner tubes, and more especially itrelates to puncture-proof inner tubes for pneumatic tires or otherinflatable bodies.

The improved inner tube is of 'the type that comprises puncture-sealingcomposition in its structure as distinguished from the compression typeof puncture-closing tube,and the chief objects of the invention are toprovide a punctureproof inner tube having improved puncture sealingcomposition incorporated in its structure; to reduce the weight of tubesof the character mentioned; to provide improved puncture-sealingproperties in the tube; and to provide an improved method of making thetube that willresult in economy and facility of manufacture, and rediicethe cost of the tube.

A salient feature of the inner tube of the invention is the eliminationof the inner layer of vulcanized rubber or other material covering theplastic puncture-sealing compound. An important advantage of the novelmethod devised is the utilization of a sealing layer which is notexcessively tacky or plastic during the manufacturing and assemblingstages, but which acquires these characteristics upon being subjected toheat at vulcanizing temperatures,as contrasted with the prior artmethods in which the puncturesealing layer is very tacky during theentire manufacturing process.

This application is a division of our copending application Serial No;642,834 flied-November 16, 1932. r r

. Of the accompanying drawing:

Figure 1 is a fragmentary side elevation of the fabricated inner tube, apart thereof being broken away and in section; Figure 2 is a section onth'e'line 2-2 ofl'igure 1; Figure 3' is a fragmentary transverse sectionontheiineS-SofPigurel;

inner tube therein. showing the action of the tube constituents whenpierced by a or the like;

and I Figurefiisaviewsimilartol'igurefshowing the action of the tube asthe nail'is withdrawn.

Referringto the. drawing. particularly Figure 3 thereof, it will be seenthat the improved inner mas. and this 18, 1934, Sub! No. 728,316

4 Claim.- (Ol. 152-347) Figure 4 is a fragmentary detail section thetread of a pneumatic tire having the improved application May tion, anda layer H of sticky, unvulcanised plastic rubber composition on theinside of the tube so disposed as to cover substantially the outerperipheral half of the tube. A

The sticky layer I I is composed of rubber composition that has beensoftened and made plastic by a chemical agent in the presence of heatduring the vulcanizing of the tube proper. Before 7 being heated thecomposition has the same phys- Per cent Phosphoric acid 2 Clay Rosin oil3 Rubber The particular softening chemical agent used is orthophosphoric acid (HaPOd :.H2O of 85% strength. The clay serves as avehicle for the phosphoric acid, the clay and acid being mixed togetherbefore being added to the other ingredients.

The rosin oil serves as a softener and tack producer, and its use hereis typical of many' rubber compounds. The several ingredients'are mixedon a'rubber mill in the usual manner.

the mixture havingthe physical characteristicsof normal compoundedrubber stock. It may be calendered into sheets and silt into strips foruse in building inner tubes.

In the structure shown in Figure -1 the layer I l covers the outerperipheral half of the body structure, which is the tread portion of thetube.

Preferably the layer ll consists of two piles of the non-vulcanizingstock, as is shown at HP, li Figures 1 and 2. A non-tacky plastic layeris provided 0 the tube as by coating with a thin film of lacqu r, paint,varnish, plasticlzed gelatin or glue, or cotton flock. This layerprevents the walls from adhering to each other during the finishingprocesses and during the packing, shipping and use of the tube. Asuitable valve stem- "is mounted in the tube. 7

The application or heat to the tube results in the vulcanization of; thebody structure II, but

vulcanizing ingredients in its composition; 'does not-vuicanize. n thecontrary the layer ll be- [comes extremely plastic, almost viscous inform,

and interiorly is very sticky. Although the nontacky'layer in the tubecauses the surface of layer 1 ll to'besomewhat less sticky sothat itwillnot adhere to the opposite wall of the tube should it come incontact therewith, it is preferable that the finished'tube be kept inlightly inflated condition.

' inner tube.

' The action of thetube in service is illustrated,

in Figures 4 and 5 wherein 20 designates the tread portion of apneumatic tire casing within which the tube is mounted, and 2|designates a nail or tack that has penetrated the tire tread pletely toseal the hole through the body struc-' ture II, as shown at 22, Figure5, and thus effectively to prevent the escape of air from the perior tothat of a puncture-sealing inner tube in which an internal layer ofvulcanized rubber covers the plastic layer. In the latter instance thevulcanized rubber, being elastic, yieldingiy grips the nail thatpunctures it, with the result that it follows the nail as the latter iswithdrawn from the hole, and thus prevents the plastic composition fromfilling the hole. The thin film of relatively non-tacky material coatedon the interior of the tube as described above is relatively non-elasticand does not follow the nail so as to interfere with the eflectivesealing puncture.

The layer ll retains its sticky character for an indefinite period andprovides a positive seal against puncture of the tube. The tube is lesscostly, lighter in weight, and provides easier'riding thanpuncture-sealing tubes of the compression type. The tube may bemanufactured with but slight departure from the usual tube-manufacturingmethods, and the invention achieves the other advantages set out in theforegoing statement of objects.

In addition to ortho-phosphoric acid it has been found that many otherchemical agents also have the power to cause the rubber to be- Phthalieanhydride Potassium The sticky stock ll adheres This sealing action isgreatly sua,1ao','a7a V the layer ll, due to the presence of thechemical" agent and absence of sulphur, accelerator or other I comepermanently tacky 'and'plastic upon being subjected to heat atvulcanizing temperatures and'may therefore be used in compounding layer1 I. The following is a representative list of these agents;

j Sulphuric acid Di-sodium hos hate Chromic acid Stannous e lo dePhosphorus pentoxide Furoic acid Para toluene sulphonic acid Chlorosulphonic acid Mono-sodium phosphate Arsenic acid Copper sulphategermanganate Meta-phosp orlc acid Phosphorus acid Boric acid Leadperoxide v Other modifications may resorted to without departing fromthe spirit of the invention or the scope of the appended claims, whichare not limited wholly to the specific construction shown or exactprocedure described.

What is claimed is:

1. An inner tube comprising an annular tubular structure of elasticrubber composition,

and a layer of non-elastic, sticky rubber composition on the interiorwall thereof, said sticky rubber composition including phosphoric acid.

2. An inner tube comprising an annular tubu ar structure of elasticrubber composition, and a layer of non-elastic, sticky rubbercomposition on the interior wall thereof, said sticky rubber compositionincluding an anti-vulcanizing chemical agent causing a permanentsoftening of the rubber when subjected to heat.

3. An inner tube comprising an annular tubular structure of elasticrubber composition, and a' circumferential coating of non-elastic,sticky composition on the interior thereof, saidsticky compositioncomprising rubber that has been subjected to heat in the presence of avulcanization retarder.

4. An inner tube comprising an annular tubular structure of elasticrubber composition, a layer of rubber composition on the interior wallthereof, which composition is permanently soft and sticky, and a thin,non-tacky non-elastic plastic film covering said sticky layer so thatthe inner surfacepf the latter is free to adhere to a puncturinginstrument for sealing a puncture in said tube as said instrument iswithdrawn therefrom.

RAYMOND S. TAYLOR. PHILIP M. TORRANCE. ROBERT'H. ANDERSON.

